Low insertion force receptacle terminal

Abstract: An electrical receptacle terminal (2) comprises a wire connection section (4), a rectangular body section (6) and a pair of cantilever beam contacts (30) extending therefrom. Insertion of a male tab between the cantilever beam contacts (30) initially prises them resiliently apart whilst passing first protrusions (34) at a forward end (32) of the terminal, and then further biases apart the cantilever beam contacts (30) when inserted between second contact dimples (38) axially rearwards of the first protrusions (34). Electrical contact is finally made between the contact dimples (38) and the male tab, which due to the short lever arm and the point contact, has a high contact pressure thereby ensuring good electrical conductivity between the dimples (38) and the tab. Certain applications may require lower currents, and the insertion force can be further reduced by providing cutouts (22,26) in the terminal body section (6) to make the resilient cantilever beam contacts (30) more supple. The latter can be done without designing new connector housings or a new terminal, and requires only a small change in the stamping process, which provides for a cost-effective solution.

Description: This invention relates to an electrical receptacle terminal that provides a high contact force yet results in a low insertion force during mating with a complementary male terminal. There is a continual demand in the electrical industry to provide electrical terminals with ever increasing current carrying capability but nevertheless being cost-effective and requiring low insertion force when mated to a complementary terminal. One of the important factors determining the current carrying capability of an electrical terminal is the resistance of the contact between mating terminals. The contact resistance is largely influenced by the presence of metal oxide layers or dirt, which increase the resistance, and the contact pressure. In order to provide a small electrical terminal that is reliable and has increased current carrying capability, the terminal should Be simple and cheap to manufacture, and have an increased contact pressure, provide a means for eliminating oxide layers between contacts by a wiping action, but nevertheless having low mating forces between complementary terminals. DE-A-1 465 461 describes an electrical receptacle contact for receiving a pin or a plate, which contact is stamped and formed from sheet metal and has a mating section comprised of opposed wiping arms each having axially spaced pairs of laterally spaced contact points projecting inwardly from the interior surface of the associated arm such that the contact points cooperate to restrict lateral movement of a pin which is inserted between the wiping arms. It is an object of this invention to provide a compact electrical receptacle terminal which is cost-effective, has a high current carrying capability and is reliable. It is another object to provide such a terminal having a simple means for adjusting the mating forces without substantial modification of the design and manufacturing thereof, yet maintaining the dimensions required for mounting in identical connector housings. The invention consists in an electrical receptacle terminal stamped and formed from sheet metal, comprising a body section having a pair of single resilient cantilever beams extending therefrom, each cantilever beam having a first protrusion proximate a male contact receiving end thereof, the first protrusions being spaced apart by a distance such that the cantilever beams are resilient biased apart during preliminary insertion of a male contact axially received therebetween and of a thickness greater than said distance, and each cantilever beam having a second contact dimple axially offset from the first protrusion towards the body section, whereby the second contact dimples are spaced apart during preliminary insertion by a distance less than said thickness of the male contact, characterized in that the body section is rectangular shaped having top, bottom and sidewalls, and the top and bottom walls of the body section comprise cutouts centrally disposed between the sidewalls and extending axially along the top and bottom walls for adjustment of the spring force of the cantilever beams by modification of the width or length of the cutouts, the arrangement being such that, during complete axial insertion of the male contact between the second contact dimples, the cantilever beams are resiliently biased further apart and electrical contact between the cantilever beams and the male contact is effected substantially by the second contact dimples. With the invention, as a male contact is mated with the receptacle terminal, the cantilever beams are resiliently biased apart in a first step by insertion of the male contact between the first protrusions and, in a second step, the cantilever beams are biased even further apart by further insertion of the male contact between the second contact dimples. Due to the rearward position of the second contact dimples with respect to the first protrusions, and therefore the shorter lever arm, the beams are biased with greater pressure against the male contact than the first protrusions would be. In order to reduce the insertion force of the male contact past the second contact dimples, they can be shaped in an axially extending oval manner so as to gradually move the contact point from a position far from the terminal body section to a position closer to the terminal body section thereby gradually changing the lever arm of the contact point. The cutouts in the top and bottom walls of the terminal body section enable the spring force of the cantilever beams to be adjusted and, therefore, the mating forces, without modification of the external dimensions of the terminal. The latter enables connectors for differing applications to be made with optimum insertion forces without large expenditure. A preferred embodiment of this invention will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 is an isometric view of an electrical receptacle terminal; Figure 2 is a top view of the terminal of Figure 1; Figure 3 is a side view of the terminal of Figure 1; Figure 4 is a bottom view of the terminal of Figure 1; and Figure 5 is a front end view of the terminal of Figure 3. Referring to Figures 1 to 5, an electrical receptacle terminal generally shown at 2, comprises a wire connection section 4 attached to a central body section 6 from which extends a contact section 8 for mating with a complementary male pin or tab terminal (not shown). The body section 6 is a rectangular shaped body comprising a pair of opposed side walls 8, a bottom wall 10 and a top wall 12 split into two halves by a seam 14 that defines the join of the sheet metal from which the terminal 2 is stamped and formed. The body section 6 also comprises a pair of resilient locking lances 16 stamped out of the side walls 8. The side walls 8 comprise cutouts 18 resulting partially from stamping out of the locking lances 16 from the side walls 8. The top wall 12 comprises a first oblong cutout 22 disposed centrally between the side walls 8 and extending in the axial direction. The bottom and top walls comprise further cutouts 24, 26 respectively, disposed axially forwards of the cutout 22 and extending to a front edge 28 of the body section 6. The contact section 8 comprises a pair of cantilever beams 30 integral with the side walls 8 and extending from the body section front edge 28 to a complementary terminal receiving end 32. The resilient cantilever beams 30 comprise at the forward-most end 32, arcuate protrusions 34 spaced apart at a distance less than the thickness of the complementary male tab or pin terminal, the arcuate contact protrusions 34 extending into outwardly flared portions 36 for guiding the complementary male terminal. The cantilever beams 30 also comprise, axially rearwards of the first protrusions 34, second contact dimples 38 that are oval shaped with the larger axis extending in the axial direction. The dimples 38 are made by embossing the sheet metal. The cross-sectional profile of the dimples 38 with respect to a section perpendicular to the axis of the terminal, is arcuate as indicated by the dotted line 40 shown in Figure 5. Projecting upwards from the side walls 8 at the rearmost position of the body section 6, are positioning tabs 42 that serve to correctly position and stabilize the terminal when mounted within a cavity of an electrical connector housing (not shown). Mating of the receptacle connector 2 and a male tab or pin terminal (not shown) will now be explained. During coupling, the male tab is directed axially between the cantilever beams 30, guided during preliminary insertion by the outwardly flared portions 36 and subsequently prising apart the beams 30 on passing the first protrusions 34. The insertion force is the greatest during the initial biasing apart of the beams 30 whilst the protrusions 34 "climb" over the forward tip of the male terminal. The male terminal is then further inserted until the front end thereof enters into contact with the second contact dimples, which are spaced apart at a distance less than the thickness of the tab due to the beam bending line starting at the forward end 28 of the body section 6 and bending progressively outwards onto the forward most end 32. The second contact dimples 38 are therefore inclined with respect to the axial direction. The male tab thus makes contact initially with a forward most end 44 of each contact dimple 38 and progressively slides across the innermost boundary 46 of the dimple 38 thereby gradually further prising apart the cantilever beams 30. Once the tab is completely inserted past the dimples 38, contact therewith is made at the rearmost end 48. Due to the inclination of each dimple 38 and its rounded profile 40, contact with the male tab is made by a "point", resulting in very high contact pressure. The latter, in addition to the wiping effect during insertion that removes any dirt or oxide layer, results in good electrical contact therebetween. The preferred embodiment of this invention as described above, has a low insertion force yet provides very high contact pressure because the cantilever beams 30 are initially prised apart at the forward-most end where the lever arm is long, and the force required therefore low, and contact is made with the second dimples 38 which are closer to the supporting structure of the beams 30, therefore have a shorter lever arm and apply a greater spring force on the male contact. To further reduce the insertion force, the second contact dimples 38 are shaped ovally in the axial direction so that the male tab gradually biases apart the cantilever beams 30 while passing from the dimples' forward-most end 44 to the rearmost end 48 where contact is finally made; the lever arm of the contact point therefore reducing gradually. During complete insertion of the male contact, electrical contact is therefore made completely, or almost completely by the second dimple contact points 48, whereby the first contact protrusions 34 are spaced apart from the male tab. As the first protrusions 34 span across the width of the cantilever beams 30, they provide a preliminary wiping action on the male terminal prior to contact with the second contact dimples. Although it would be desirable to have the highest possible contact pressure for good electrical conductivity, this also means that the insertion force will be correspondingly high. In order to further reduce the insertion force, the contact pressure could be reduced to an optimum value ensuring sufficient conductivity for the electrical current that is specified. This is obviously not always the same, depending on the application, and it is therefore possible in many cases to reduce the contact pressure, thereby further reducing the insertion force. This can be achieved without changing the terminal material or redesigning the terminal, by providing the cutouts 22, 24, 26 in the bottom and top walls and the cutouts 18 in the side walls 8. These cutouts reduce the rigidity of the structure supporting the cantilever beams 30, thereby making the beams 30 more supple. By varying the length and the width of the cutouts 18, 22, 24, 26, the resiliency of the cantilever beams 30 can be reduced to an optimum value sufficient to ensure the specified current, yet providing the lowest insertion force. The advantage of the latter is the maintenance of the terminal exterior dimensions which means that connectors for differing applications can be produced with the same connector housings and male terminals, whilst only modifying the receptacle terminals by punching different sized cutouts; the latter requiring only minor modification of the stamping tool and procedure. Advantageously therefore, the invention as described above procures a very high contact pressure, due to: the point contact, the effective wiping action, and the high spring force; whilst maintaining the insertion force of the complementary male terminal low by providing the first protrusions 34 having a long lever arm and effectuating initial biasing apart of the contact beams thereby. The insertion force is further reduced by providing an oval shaped contact dimple that progressively engages the male terminal. In order to produce terminals for different applications, but having the lowest insertion forces, cutouts in the terminal body section can be provided to render the contact beams more supple. The latter enables the production of cost-effective connectors with minimal mating forces.

Claims: An electrical receptacle terminal stamped and formed from sheet metal, comprising a body section (6) having a pair of single resilient cantilever beams (30) extending therefrom, each cantilever beam (30) having a first protrusion (34) proximate a male contact receiving end (32) thereof, the first protrusions being spaced apart by a distance such that the cantilever beams are resiliently biased apart during preliminary insertion of a male contact axially received therebetween and of a thickness greater than said distance, and each cantilever beam (30) having a second contact dimple (38) axially offset from the first protrusion (34) towards the body section (6), whereby the second contact dimples (38) are spaced apart during preliminary insertion by a distance less than said thickness of the male contact, characterized in that the body section (6) is rectangular shaped having top (12), bottom (10) and sidewalls (8), and the top (12) and bottom (10) walls of the body section (6) comprise cutouts (22, 24, 26)centrally disposed between the sidewalls (8) and extending axially along the top and bottom walls for adjustment of the spring force of the cantilever beams (30) by modification of the width or length of the cutouts (22, 24, 26), the arrangement being such that, during complete axial insertion of the male contact between the second contact dimples (38), the cantilever beams (30) are resiliently biased further apart and electrical contact between the cantilever beams (30) and the male contact is effected substantially by the second contact dimples (38). The terminal of claim 1 wherein each of the first protrusions (34) comprises an arcuate contact section (34) extending into a flared lead-in portion (36) towards the male contact receiving end (32) for guiding the male contact therebetween during preliminary insertion. The terminal of claim 2 wherein the arcuate contact section (34) and flared lead-in portion (36) extend across substantially the whole width of the cantilever beam (30). The terminal of any preceding claim wherein the cantilever beams (30) extend only from opposed sidewalls (8) of the body section (6). The terminal of any preceding claim wherein the second contact dimples (38) are embossed. The terminal of any preceding claim wherein the shape of each second contact dimple (38) is oval, whereby the largest dimension is substantially axial. The terminal of any preceding claim wherein the contact between each second contact dimple (38) and the male contact is substantially a point contact. The terminal of any preceding claim wherein the second contact dimples (38) are disposed between lines defined by axially generating extremities of the first protrusions (34). The terminal of any preceding claim wherein at least one of the cutouts (24, 26) extends rearwardly from a front edge (28) of the top (12) or bottom (10) wall or both. The terminal of any preceding claim wherein the sidewalls (8) have cutouts (18) resulting from the formation of resilient locking lances (16). The terminal of claim 10 wherein the sidewall cutouts (18) are increased in width or axial length or both, with respect to the locking lance (16), for adjustment of the spring force of the cantilever beams (30).

Inventors: OP TEN BERG ROY HENRICUS, OP TEN BERG, ROY HENRICUS
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1994
Main classification: H01R13
IPC codes: H01R13